Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.50	13.304%	$112.7375	$112.74	$112.75	$112.70
Purchase #2	$104.70	7.660%	$112.72	$112.72	$112.70	$112.70
Purchase #3	$75.26	3.496%	$77.8911	$77.89	$77.90	$77.90
Purchase #4	$177.57	7.682%	$191.2109	$191.21	$191.20	$191.20
Purchase #5	$45.51	4.740%	$47.6672	$47.67	$47.65	$47.70
Purchase #6	$196.91	12.404%	$221.3347	$221.33	$221.35	$221.30
Purchase #7	$234.58	8.541%	$254.6155	$254.62	$254.60	$254.60
7 purchase totals =	$934.03		$1,018.1769	$1,018.18	$1,018.15	$1,018.10